Electrostatic registration for contact printing

ABSTRACT

A contact printing apparatus for accurately and precisely maintaining in registry a master image-bearing transparent film and a light-sensitive duplicate. In one embodiment, the master and duplicate comprise two film strips being initially wound on separate supply reels and transported through an exposure zone to take-up reels by a drive mechanism. A pair of high voltage rollers are disposed upstream of the exposure zone in contact with the moving master and duplicate so as to electrostatically charge them causing strong attraction and adherence therebetween. A discharge device is provided downstream of the exposure zone so as to prevent any scintillation when the master and duplicate are separated.

United States Patent [151 3,661,457 Frech 1 May 9, 1972 [541 ELECTROSTATIC REGISTRATION FOR 3,437,336 4/1969 Enke et al ..3ss/3 x CONTACT PRINTING Roger A. Frech, Spring Valley, Calif.

Extek Microsystems, Inc., Van Nuys, Calif.

Mar, 6, 1970 Inventor:

Assignee:

Filed:

Appl. No.:

References Cited UNITED STATES PATENTS Primary Examiner-Samuel S. Matthews Assistant Examiner-Richard A. Wintercorn AttorneyNilsson, Robbins, Wills & Berliner ABSTRACT herence therebetween. A discharge device is provided downstream of the exposure zone so as to prevent any scintillation when the master and duplicate are separated.

11 Claims, 5 Drawing Figures A.C. SOURCE ELECTROSTATIC REGISTRATION roR conrxcr I PRINTING BACKGROUND OF THE INVENTION AND PRIOR ART put devices, on microfilm and microfiche has given rise to the need for. rapidly and inexpensively producing duplicates of such microfilm information. Such information may be stored on film strips or on cards," i.e., discrete pieces of material. The printing may be from a film strip to a duplicate strip or to a card or from a card to duplicate card or strip. The strip may be rolled. The duplicate may be opaque ortransparent.

For purposes of convenience and description, the term master is used to mean an image or character bearing transparent piece of dielectric material in the form of a roll, strip, web or card. The term duplicate" is used to mean an initially unexposed, light-sensitive dielectric material to which an image is transferred during operation of the contact printing apparatus and in the form of a strip or card. The term master is used to refer to one or more piecesof material from which the images are simultaneously transferred to single duplicate. For example, two master strips of 16 mm. film may be fed in side by side relation together with a duplicate strip of 35 mm. film.

Various apparatus have been provided in the prior art in which strips are moved through a planar exposure zone and are maintained in registry by the application of a vacuum between the strips for compressing. the strips through atmospheric pressure thereby preventing relative longitudinal movement therebetween. A more recently suggested means for maintaining the strips in registration during movement is by electrostatically charging the two strips so that they strongly attract one another and prevent movement therebetween. The suggested use of corona discharge devices for producing the electrostatic charge, however, has been found to produce large amounts of ozone during continuous and prolonged operation of the apparatuswhich maybe a safety hazard. Moreover, the light generated by a corona discharge device may deleteriously afiect extremely light-sensitive duplicate strips.

SUMMARY OF THE INVENTION It is a general object of the presentinvention to provide an apparatus for contact printing a duplicate from a transparent, image-bearing master by passing the materials through an exposure zone, the materials being electrostatically charged so as to adhere to one another while minimizing the production of ozone. I

It is another object of the present invention to provide an apparatus as above described wherein the electrostatic charging means comprises a pair of contact rollers which are connected to a do voltage source and which are so spaced in relation to the master and duplicate so as to prevent the occurrence of an air path sparkover between the rollers.

Yet another object of the present invention is to provide an apparatus of the last-described type wherein means is provided for electrostatically charging the master and duplicate by at least one pair of electrically conductive rollers arranged in staggered longitudinal spaced relation.

One more object of the present invention is to provide an apparatus of the described type wherein the possibility of scintillation is reduced or eliminated by discharging the master and duplicate after they pass through the exposure zone before they are separated. I

Generally, in a contact printing apparatus, the present in-- vention provides means for electrostatically charging master and duplicate pieces of dielectric material as they are simultaneously moved through an exposure zone to produce attraction and adherence during exposure, the means including rotatably lupportedelectrically conductive rollers in contact with the outer surfaces of the two pieces of material and a source of dc. voltage connected to the rollers, the rollers being arranged in relation to one another so as to prevent sparkover across the air path between the rollers.

BRIEF DESCRIPTION or "nu; DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, there is diagrammatically shown an exemplary embodiment of an apparatus for contact printing of a duplicatelight-sensitive continuousstrip from a transparent image-bearing continuous master strip of film. It will be understood that the apparatus disclosed is adopted for use with continuous strip type of master and duplicate and includes transport means suitable therefonWhere the master or duplicate is a card or short length of dielectric material, other transport means, known to those having ordinary skillin the art, may be provided.

Generally, apparatus for handling'a master and duplicate of the continuous strip type comprises a frame (not shown) supporting a pair of supply reels 20, 21 around which the master and duplicate strips are initially wound, and a pair of take-up reels 22, 23 on which the strips are finally wound. Such reels are entirely conventional, the take-up reels being driven and a suitable clutch or brake mechanism provided for the supply reels. 1

view taken along the plane Ill-Ill of The master and duplicate strips are drawn from the supply I which may be adjustable to the desired speed of film movement. The take-up reels 22 and 23 are also motor driven at a speed compatible with the speed of the metering rollers and upon which the film is finally wound.

Means 30 for exposing the master and duplicate is positioned above the strips and defines a planar exposure zone. Such means will be compatible with the type of materials being used in the printing operation. For example, an actinic light source, such as a mercury lamp, or a plurality of such lamps, will be employed where the duplicate is a light-sensitive, diazo-sensitized film. It will of course be understood that the exposed duplicate on reel 23 may be immediately or later developed in known manner in accordance with the particular emulsion used, or alternatively, suitable developing means may be incorporated into the contact printing apparatus itself.

The details of such developing means are well known in the art and form no part of the present invention.

While not shown, the strips may be laterally guided by one lers, indicated generally at 45, and a source 50 of d.c. voltage. The frame 36 generally comprises a pair of sidewalls 37, 38 supported in spaced apart relation by a base wall 39. The master and duplicate film strips pass through a pair of rubber coated guide rollers indicated generally at 40 and rotatably supported at the forward end of the sidewalls 37, 38. The frame 36 may be constructed of metal, in which event, each of the sidewalls 37, 38 are provided with a slot 41 in which is disposed a pair of mounting blocks 42, 43 of insulating material.

The roller pair 45 including electrically conductive rollers, which may be constructed of metal, or a conductive material, such as rubber, are indicated at 46 and 47. Each of the rollers 46 and 47 are mounted on axles 48, 49, respectively, which are supported by sidewalls 37, 38. More particularly, the axles 48, 49 for the rollers 46, 47 are supported in the blocks of insulating material 42, 43 as seen best in FIG. 4. The rollers 46, 47 are supported in vertically spaced apart relation so as to receive the master and duplicate strips therebetween and remain in contact engagement with such strips. The axle 48 of roller 46 is mounted in slidably movable block 42. A spring 44 is mounted on the frame sidewall 38 and biases the block 42 downwardly toward block 43 which supports roller 47. Thus, the rollers will accommodate films of different thickness and will remain in intimate contact with the outer surfaces of the strips notwithstanding variations in thickness due to nonnal manufacturing tolerances. After the strips pass from between rollers 46, 47, the rollers are biased into contact to short out the power source as an operator safety measure.

The dc voltage source 50 is connected to rollers 46, 47 through wires, indicated generally at 51, which may be connected to the rollers 46, 47 through brushes 52, 53 suitably fixed to the frame 36 and in rotatable contact with the ends of the axles 48, 49. Of course, the voltage source may be connected to the rotating rollers 46, 47 in any manner which is well known in the art for passing an electrical current from a stationary to a rotating body. Of course, it will also be understood that one of the rollers may be positively charged while the other roller may be grounded rather than connection to the opposite poles of the d.c. source of voltage which is suitably grounded. Such d.c. voltage source may be in the range of 4,000 to 8,000 volts with a current of a few microamperes. The rollers 46, 47 will therefore create a potential across the film strips so as to produce opposite electrostatic surface charges on the strips which will cause strong attraction and adherence therebetween.

It is an important feature of this invention that the use of electrically conductive contact cylinders in engagement with the strips obviates the use of corona discharge units which while supplying an electrostatic charge as required, create ozone which is both dangerous to health and a safety hazard. It has been found that when the contact rollers have a width which is substantially equal to the width of the film strips passing therebetween sparkover may result through the air path between the ends of the rollers 46, 47. The resistance to sparkover or breakdown of the air path between the electrically conductive roller ends, depends upon humidity and altitude conditions. Since the resistance to sparkover is a function not only of the dielectric constant of the path over which the potential is impressed, but is also a function of the distance between the electrically conductive surfaces, the resistance to sparkover may be increased by spacing the ends of the conductive rollers from the edge of the strips so as to increase the length of the air path. Supression of sparkover will preclude degradation of the strip edges and will additionally eliminate scintillation which would have an adverse effect upon the light-sensitive duplicate strip.

The contact printing apparatus of the present invention may also include, where static discharge upon strip separation is a problem, means 70 for discharging a longitudinal portion of the continuous strips after such portion has passed through the exposure zone. In the exemplary embodiment, such means comprises a source 71 of ac. voltage electrically connected to the drive rollers 25, as seen in FIG. I, to produce an ac. electrostatic field to discharge the strips. The voltage potential chosen is substantially equal to the voltage impressed upon the strips by the electrostatic charging means. In this manner, the portions of the continuous strips which have passed through the exposure zone will be discharged such that when the strips are separated (immediately subsequent to the drive rollers 25) no arcing or scintillation will result which would degrade the light-sensitive duplicate strip by causing black or white spots, splotches, streaks or other markings which result from static discharge as is commonly known in the photographic arts.

In the alternative embodiment of FIG. 5, there is shown another arrangement ofconductive contact rollers for applying opposite electrostatic charges to the master and duplicate strips. A charge is applied to the master through roller 65 in contact with the upper surface of the master and an opposite charge is applied to the duplicate strip through roller 66 in contact with the lower surface thereof. Intimate contact pressure is maintained by causing the strips to partially wrap about the rollers in a sinuous path so that tension on the strips will produce contact pressure. The rollers extend to or beyond the edges of the strips. It will be immediately appreciated that the oppositely charged rollers are spaced apart such that air gap sparkover is prevented.

it will now be seen that the contact printing apparatus of the present invention provides electrostatic charging means which produces strong attraction and adhesion between the two strips while minimizing or eliminating the production of ozone, and discharge means which precludes the occurrence of scintillation or arcing between the strips as they are separated to maintain the integrity of the light-sensitive strip. Other modifications and variations of the present invention are possible in light of the above teachings. it is therefore to be understood that the invention may be practiced otherwise than as specifically described in relation to the exemplary embodiments discussed.

I claim:

1. In a contact printing apparatus comprising means for supporting an image-bearing master film and a light-sensitive duplicate, means for exposing the master and duplicate in a planar zone, and means for moving the master and duplicate through the exposure zone, the provision of:

means in the path of movement of said master and duplicate prior to said exposure zone for bringing said master and duplicate into contact with each other and electrostatically charging at least one of the master and duplicate while in said contact to cause attraction and adherence therebetween during exposure thereof, said means including a frame, a source of d.c. voltage, and a pair of spaced apart electrically conductive rollers supported by said frame so as to contact the outer surfaces of said master and duplicate, at least one of said rollers connected to said voltage source to create a potential between said rollers, said rollers being arranged in spaced relation with respect to one another so as to prevent sparkover across the air path between the portions of the oppositely charged rollers in closest spaced relation.

2. In a contact printing apparatus comprising means for supporting an image-bearing master film and a light-sensitive duplicate, means for exposing the master and duplicate in a planar zone, and means for moving the master and duplicate through the exposure zone, the provision of:

means for electrostatically charging at least one of the master and duplicate to cause attraction and adherence therebetween during exposure thereof, said means including a frame, a source of d.c. voltage, and a pair of spaced apart electrically conductive rollers supported by said frame so as to contact the outer surfaces of said master and duplicate, at least one of said rollers connected to said voltage source to create a potential between said rollers, said rollers being arrayed in opposed spaced relation on opposite sides of said master and duplicate, said rollers having a width less than the width of said master and duplicate, said rollers having ends spaced inwardly from the edges of said master and duplicate so as to increase the length of the air path between said roller ends to prevent sparkover thereacross.

3. The provision of claim 1 wherein said rollers are arranged in longitudinally spaced relation.

4. In a contact printing apparatus comprising means for supporting an image-bearing master film and a light-sensitive duplicate, means for exposing the master and duplicate in a planar zone, and means for moving the master and duplicate through the exposure zone, the provision of:

means for electrostatically charging at least one of the master and duplicate to cause attraction and adherence therebetween during exposure thereof, said means ineluding a source of dc. voltage, a pair of spaced apart electrically conductive rollers supported by said frame so as to contact the outer surfaces of said master and duplicate, at least one of said rollers connected to said voltage source to create a potential between said rollers, said rollers being arranged in spaced relation with respect to one another so as to prevent sparkover across the air path between the portions of the oppositely charged rollers in closest spaced relation, and means for biasing the master and duplicate outer surfaces in contact with said roller.

5. In a contact printing apparatus comprising means for supporting an image-bearing master film and a light-sensitive duplicate, means for exposing the master and duplicate in a planar zone, and means for moving the master and duplicate through the exposure zone, the provision of: 7

means for electrostatically charging at least one of the master and duplicate to cause attraction and adherence therebetween during exposure thereof, said means including a frame, a source of dc. voltage, a pair of spaced apart electrically conductive rollers supported by said frame so as to contact the outer surfaces of said master.

and duplicate, at least one of said rollers connected to said voltage source to create a potential between said rollers, said rollers arranged in spaced relation with respect to one another so as to prevent sparkover across the air path between the portions of the oppositely charged rollers in closest spaced relation, and means for discharging a longitudinal portion of said master and duplicate after said portion thereof has passed through said exposure zone so as to prevent scintillation when said master and duplicate are separated thereby precluding inadvertent exposure of said light-sensitive duplicate.

6. The contact printing apparatus of claim 5 wherein said means for discharging said master and duplicate comprises an ac. voltage source coupled to a pair of contact rollers, said source providing a peak voltage substantially equal to said dc voltage.

7. In a contact printing apparatus comprising supply means for supplying image-bearing transparent master and light-sensitive duplicate continuous strips and take-up, means for taking up said master and duplicate strips, means for moving the strips from the supply means to the take-up means, and means for exposing the film strips in a planar zone, the provision of:

means in the path of movement of said master and duplicate prior to said exposure zone for bringing said master and duplicate into contact with each other and electrostatically charging at least one of said strips while in said contact to cause attraction and adherence therebetween during exposure thereof, said means including a frame, a source of dc. voltage, and a pair of spaced apart electrically conductive rollers supported by said frame so as to receive the strips therebetween in contact with the outer surfaces thereof, at least one of said rollers connected to said voltage source to create a potential difference between the rollers, said rollers being spaced so as to prevent arcing across the air path between the portions of the rollers i n closest spaced relation. 8. The provision of claim 7 wherein said rollers are spaced apart in the general direction of movement of said master and duplicate and on opposite sides of said master and duplicate.

9. In a contact printing apparatus comprising supply means for supplying image-bearing transparent master and light-sensitive duplicate continuous strips and take-up means for taking up said master and duplicate strips, means for moving the strips from the supply means to the take-up means, and means for exposing the film strips in a planar zone, the provision of:

means for electrostatically charging said strips to cause attraction and adherence therebetween during exposure thereof, said means including a frame, a source of dc. voltage, and a pair of spaced apart electrically conductive rollers supported by said frame so as to receive the strips therebetween in contact with the outer surfaces thereof, at least one of said rollers connected to said voltage source to create a potential difference between the rollers, said rollers being spaced apart so as to prevent arcing across the air path between the portions of the rollers in closest spaced relation, said rollers having a width less than the width of said master and duplicate strips so as to be spaced inwardly from the edges of said master and duplicate strips to increase the length of the air path between the roller ends so as to prevent arcing.

10. The provision of claim 1 wherein said rollers are arranged in opposed relation on opposite sides of said master and duplicate, at least one of aid rollers having a width less than the width of at least one of said master or duplicate and having its strip-contacting edges spaced inwardly from the edges of said one strip so as to increase the length of the air path between the ends of the opposed rollers.

l l. The provision of claim 7 wherein at least one of said rollers has a width less than the width of at least one of said master or duplicate strips and has its strip'contacting edges spaced inwardly from the edges of said one strip to increase the length of the air path between the ends of the opposed rollers to prevent arcing. 

1. In a contact printing apparatus comprising means for supporting an image-bearing master film and a light-sensitive duplicate, means for exposing the master and duplicate in a planar zone, and means for moving the master and duplicate throuGh the exposure zone, the provision of: means in the path of movement of said master and duplicate prior to said exposure zone for bringing said master and duplicate into contact with each other and electrostatically charging at least one of the master and duplicate while in said contact to cause attraction and adherence therebetween during exposure thereof, said means including a frame, a source of d.c. voltage, and a pair of spaced apart electrically conductive rollers supported by said frame so as to contact the outer surfaces of said master and duplicate, at least one of said rollers connected to said voltage source to create a potential between said rollers, said rollers being arranged in spaced relation with respect to one another so as to prevent sparkover across the air path between the portions of the oppositely charged rollers in closest spaced relation.
 2. In a contact printing apparatus comprising means for supporting an image-bearing master film and a light-sensitive duplicate, means for exposing the master and duplicate in a planar zone, and means for moving the master and duplicate through the exposure zone, the provision of: means for electrostatically charging at least one of the master and duplicate to cause attraction and adherence therebetween during exposure thereof, said means including a frame, a source of d.c. voltage, and a pair of spaced apart electrically conductive rollers supported by said frame so as to contact the outer surfaces of said master and duplicate, at least one of said rollers connected to said voltage source to create a potential between said rollers, said rollers being arrayed in opposed spaced relation on opposite sides of said master and duplicate, said rollers having a width less than the width of said master and duplicate, said rollers having ends spaced inwardly from the edges of said master and duplicate so as to increase the length of the air path between said roller ends to prevent sparkover thereacross.
 3. The provision of claim 1 wherein said rollers are arranged in longitudinally spaced relation.
 4. In a contact printing apparatus comprising means for supporting an image-bearing master film and a light-sensitive duplicate, means for exposing the master and duplicate in a planar zone, and means for moving the master and duplicate through the exposure zone, the provision of: means for electrostatically charging at least one of the master and duplicate to cause attraction and adherence therebetween during exposure thereof, said means including a source of d.c. voltage, a pair of spaced apart electrically conductive rollers supported by said frame so as to contact the outer surfaces of said master and duplicate, at least one of said rollers connected to said voltage source to create a potential between said rollers, said rollers being arranged in spaced relation with respect to one another so as to prevent sparkover across the air path between the portions of the oppositely charged rollers in closest spaced relation, and means for biasing the master and duplicate outer surfaces in contact with said roller.
 5. In a contact printing apparatus comprising means for supporting an image-bearing master film and a light-sensitive duplicate, means for exposing the master and duplicate in a planar zone, and means for moving the master and duplicate through the exposure zone, the provision of: means for electrostatically charging at least one of the master and duplicate to cause attraction and adherence therebetween during exposure thereof, said means including a frame, a source of d.c. voltage, a pair of spaced apart electrically conductive rollers supported by said frame so as to contact the outer surfaces of said master and duplicate, at least one of said rollers connected to said voltage source to create a potential between said rollers, said rollers arranged in spaced relation with respect to one another so as to prevent sparkover across the air path between the portions of the oppositely charged rollers in closest spaced relation, and means for discharging a longitudinal portion of said master and duplicate after said portion thereof has passed through said exposure zone so as to prevent scintillation when said master and duplicate are separated thereby precluding inadvertent exposure of said light-sensitive duplicate.
 6. The contact printing apparatus of claim 5 wherein said means for discharging said master and duplicate comprises an a.c. voltage source coupled to a pair of contact rollers, said source providing a peak voltage substantially equal to said d.c. voltage.
 7. In a contact printing apparatus comprising supply means for supplying image-bearing transparent master and light-sensitive duplicate continuous strips and take-up, means for taking up said master and duplicate strips, means for moving the strips from the supply means to the take-up means, and means for exposing the film strips in a planar zone, the provision of: means in the path of movement of said master and duplicate prior to said exposure zone for bringing said master and duplicate into contact with each other and electrostatically charging at least one of said strips while in said contact to cause attraction and adherence therebetween during exposure thereof, said means including a frame, a source of d.c. voltage, and a pair of spaced apart electrically conductive rollers supported by said frame so as to receive the strips therebetween in contact with the outer surfaces thereof, at least one of said rollers connected to said voltage source to create a potential difference between the rollers, said rollers being spaced so as to prevent arcing across the air path between the portions of the rollers in closest spaced relation.
 8. The provision of claim 7 wherein said rollers are spaced apart in the general direction of movement of said master and duplicate and on opposite sides of said master and duplicate.
 9. In a contact printing apparatus comprising supply means for supplying image-bearing transparent master and light-sensitive duplicate continuous strips and take-up means for taking up said master and duplicate strips, means for moving the strips from the supply means to the take-up means, and means for exposing the film strips in a planar zone, the provision of: means for electrostatically charging said strips to cause attraction and adherence therebetween during exposure thereof, said means including a frame, a source of d.c. voltage, and a pair of spaced apart electrically conductive rollers supported by said frame so as to receive the strips therebetween in contact with the outer surfaces thereof, at least one of said rollers connected to said voltage source to create a potential difference between the rollers, said rollers being spaced apart so as to prevent arcing across the air path between the portions of the rollers in closest spaced relation, said rollers having a width less than the width of said master and duplicate strips so as to be spaced inwardly from the edges of said master and duplicate strips to increase the length of the air path between the roller ends so as to prevent arcing.
 10. The provision of claim 1 wherein said rollers are arranged in opposed relation on opposite sides of said master and duplicate, at least one of aid rollers having a width less than the width of at least one of said master or duplicate and having its strip-contacting edges spaced inwardly from the edges of said one strip so as to increase the length of the air path between the ends of the opposed rollers.
 11. The provision of claim 7 wherein at least one of said rollers has a width less than the width of at least one of said master or duplicate strips and has its strip-contacting edges spaced inwardly from the edges of said one strip to increase the length of the air path between the ends of the opposed rollers to prevent arcing. 